1. Field of the Invention
The present invention relates generally to an electromagnetic sensing apparatus in a touch screen display, and more particularly, to an electromagnetic sensing apparatus for sensing an external input from a user by sensing ElectroMagnetic Resonance (EMR).
2. Description of the Related Art
Generally, a user can enter inputs into a device including a touch screen display by touching the screen with a user's body part, e.g., finger, or an EMR pen.
A touch screen display that receives inputs from a user's finger is commonly referred to as a capacitive type touch screen. In general, a capacitive type touch screen includes transparent electrodes and condensers. When the user touches the touch screen, a mechanical displacement occurs in an area of a condenser, such that the touch may be sensed based on the resulting changed capacity of the condenser.
However, the capacitive type touch screen always requires a specific pressure or displacement caused by the user's touch, which may cause user inconvenience.
An EMR type touch screen controls generation of electromagnetic waves by passing current through a loop coil disposed on a Printed Circuit Board (PCB) and controls absorption of the electromagnetic waves into an EMR pen. For example, the EMR pen includes a condenser and a loop, and emits the absorbed electromagnetic waves in a specific frequency. Specifically, the electromagnetic waves emitted from the EMR pen are absorbed again into the loop coil of the PCB such that a position near to the EMR pen can be determined based on the absorbed electromagnetic waves.
FIG. 1A illustrates a communication device with an electromagnetic sensing circuit operating in a conventional EMR scheme.
Referring to FIG. 1A, the communication device 100 includes a display 110 and soft keys 120. The display 110 displays information to a user and may operate in either an EMR scheme or a capacitive scheme.
The soft keys 120 are a user interface provided separately from the display 110, which enable the user to intuitively perform basic functions such as back, cancel, menu display control, etc. Conventionally, the soft keys 120 operate only in the capacitive type scheme due to limitations on accommodation of capacitive sensors and EMR sensors arranged under transparent electrodes. Soft keys having EMR sensors built in them have not been specified yet.
FIG. 1B illustrates a plurality of loops arranged in a display of the communication device illustrated in FIG. 1A. Specifically, FIG. 1B illustrates a plurality of loops 131 to 134 arranged in the display 110.
Referring to FIG. 1B, the plurality of loops 131 to 134 may be arranged overlapping with each other. When a user places an EMR pen close the display 110, the loops 131 to 134 may sense an electromagnetic field from the EMR pen, thereby identifying a specific position on the display 110.
FIG. 1C is a graph illustrating induced current output from the plurality of loops illustrated in FIG. 1B.
Referring to FIG. 1C, each of the loops 131 to 134 may output current induced by the sensed electromagnetic field. A loop nearer to the EMR pen may sense a large-amplitude electromagnetic wave and emit induced current corresponding to the sensed electromagnetic wave. Therefore, induced currents with different magnitudes may be output as illustrated in FIG. 1C.
Accordingly, a microprocessor (not shown) of the communication device 100 determines a peak by interpolating the magnitudes of the output induced current and thus, may determine a user-input position on the display.
As described above, because only the capacitive scheme is adopted for the soft keys 120, users should input commands by touching the soft keys 120 with their fingers.
Further, even if channels are added to sense EMR on the soft keys 120, the numbers of channels and coils, as well as a size of the control circuit, increase. However, The larger control circuit and the increased number of coils increase manufacturing costs.